Electric heating unit



March 31. 1925. 1,531,671

W. C. LINDEMANN ELECTRIC HEATING UNIT Filed April 22, 1922 83 flttomm;

Patented Mar. 31 1925.

UNITED "STATES PATENT OFFICE WALTER C. OF MILWATJ'KEE, WISCONSIN, ASSIGNOR TO A. J. LINDEMANN & HOVEBSON COMPANY, F MILWAUKEE, WISCONSIN.

ELECTRIC r rmrmo UNIT.

Application filed April 22, 1922. Serial No. 555,990.

To all whom it may concern:

Be it known that I, WALTER C. LINDE- MANN, a citizen of the United States, and a resident of the city of Milwaukee, in the county of Milwaukee, State of Wisconsin, have invented certain new and useful -Improvements in Electric Heating Units, of which the following is a specification.

The improvements relate to electric heating units, such as are adapted to be used for heating and cooking food, and for other domestic purposes and its objects are, among others, to provide a highly efficient unit of this character of extremely simple, strong, and durable construction. in which the electric resistance wires or the like are securely held and positioned, and may be installed, removed and replaced without difficulty and without the slightest injury to the said element or any other part of the unit.

The improvements are illustrated in the accompanying drawings, in which Figure 1 is a plan of an electric heating device embodying the improvements; Fig. 2 is a vertical section of the same on the line 22 of Fig. 1 looking in the direction indicated by the arrows in that figure.

The plate or frame 1 consists of a single piece of material, preferably brick, porcelain, or insulated metal, and in this is formed a continuous groove 2 of sinuous form. The plate however may be made in sections secured together by suitable means and the groove member of any desired form. At the bends or corners of the groove are projecting portions 3 which are undercut, as shown at 4, so as to form tongues, and opposite these projecting portions is an enlargement or widened pgrt of the groove, so that the distance tween the outer extremity of each projecting portion and the o posite edge of the groove at the top is su cient for the electric resistance I material 6 to pass therethroughinto the bot tom of the groove, the groove being tapered downwardly as shown at 7, but having a greater bevel or taper o posite the proLeocting portions than at ot er parts. A re 8 eitends from the bottomof the groove through; to the under surface of the late 1 under each projecting portionand a ords an opportunity for the insertion in the mold of a part extending throughaspace represented by the opening to form the lower surface of the projecting portion or overhanging tongue 3. It'also provides for upward movement of air at this point and for drainage of the groove. The tapered portion 7 also permits upward radiation and the upward passage of heated air. The making of the plate with its holding devices in one piece or section secures great advantages, and while the device may be made in two or more sections, the provision of means for making it in one section is important.

The electric resistance element 6 consists of a piece of wire of one of the well known alloys suitable for that purpose curled spirally but any other satisfactory form may be employed, and the terminals 5 are passed through holes 9 extending to the bottom of the plate where they may be connected with a lamp circuit or other source of electric current. It is placed in position by running it around the groove and passing it to the bottom thereof under a moderate tension, so that at the bends of the groove it will snap in under the tongues 3 and be held thereby against upward movement. As the wire of the element "is coiled, and has a certain amount of resil ence it will remain under tension, when its ends are passed through the holes 9, and this tension tends constantly to move it at the bends down to the bottom of the groove.

The wire will keep its position, however,

and even though the plate be inverted and shaken, as it may be, to remove particles that may have lodged in the groove, since the bending of the coiled wire at the corners causes it to bind to a certain extent under the tongues.

It will be seen that the structure is one of extreme simplicity and great strength and durability with a high heating capacity, and that the radiation of heat is substantially uniform over its entire surface, the

resistance element being exposed throughout its entire length. It will also be seen that the electric resistance wire may be appliedor removed in a. few moments, and without making or releasing any holding means requirin manipulation, and without the use of too s, and that when the parts are assembled they are securely connected and held in position. For all ordinary cleanin pur poses the. resistance wire need not reproperdistribution of heat.

moved but may be brushed, and the heating unit reversed and shaken to remove particles that may have lodged thereon'or in the groove. If however it becomes necessary to remove the wires this may be done quickly and easily and by an unskilled person, after which it may be restored with equal facility. y In the drawings a single groove is shown, but more than one groove maybe employed in a single unit. For instance grooves may be made parallel with each other; or otherwise made in the plate so as to harmonize in construction and design and give the The over-hanging'portions are preferably located at the bends or corners, but any other location which will enable them to perform their functions to advantage may be used.

- \Vhat I claim is:

1. An electric heating unit comprising a plate having therein and extending around the same a substantially continuous multicurved groove, an electric resistance element located in said groove and following the curves thereof. said grooves having communicating substantially radial and arclike portions.

2. In a device such as that specified in claim 1,'terminals for the electric resistance element in proximity to each other at one portion of the groove.

' 3. A device such as that specified in claim 1, in which the plate is made of a single piece of material;

4. A device such as that specified in claim 1, in which the plate made of a single piece of insulating material. a

5. A device such as that specified in claim 1, in which the electric resistance element consists of a wire bent or coiled and held in the groove under tension.

6. A device such as that specified in claim 1, in which portions of the plate extend over the said groove at certain points in its length and overlie portions of the electric resistance element therein.

7. A device such as that specified in claim 6, in which the groove has recessed walls opposite the projecting portions. v

8. A device'such as that specified in claim 6, in which the said extending portions are composed of members overhanging the lower part of the' groove at its bends.

9. An electric heating unit comprising a plate of insulating material having therein a continuous groove with foliate or leaf-like reaches in substantiallyradial arrangement, an electric resistance element extending from one portion of said groove throughout its length and back to the same portion.

10. An electric heating device comprising a-platc ot'insulating material having therein a groove in the form of a series of loops with inner and outer bends. said loops being disposed on substantially radial lines, said plate having portions extending over the groove at its inner and outer bends and an attenuated resistance element in said groove.

11. An electric heating device comprising a plate of insulating material having therein a groove in the form of a series of loops with inner and outer bends, said loops being disposed on substantially radial lines. said plate having portions extending over the groove at its inner and outer bends and an attentuated resistance element in said groove, said groove having laterally extending portions at its bends opposite the said overhanging portions.

12. An electric heating device comprising a plate of insulating material having therein a groove in the form'ot' a series of loops with inner and outerbends, said loops being disposed on substantially radial lines, said platehaving portions extending over the groove at its inner and outer bends and an attenuated resistance element in said groove, said plate also having openings at intervals extending from the lower part of the groove to the bottom of the plate.

Witness my hand this 18th day of April,

.1922, at the city of Milwaukee, in the county of Milwaukee, State of Wisconsin.

WALTER C. -LINDEMANN. 

